The use of metal neutralized sulfonated polymers such as zinc sulfonated EPDM terpolymer as thermoplastic elastomers has been described in many U.S. Patents such as Nos. 3,974,240; 3,974,241; 3,642,728; 3,836,511; 3,870,841; and 3,847,854, which are all herein incorporated by reference. While these and related compositions exhibit good physical properties, their melt flow at elevated temperatures has been generally defensive. Attempts at improvements in the flow characteristics of these compositions have generally resulted in an adverse effect on physical properties. In general, a proper balance of physical and rheological properties necessary for an extrudable or injection moldable composition has been unattaintable although these compositions have been readily adaptable for compression molding processes. For example, in U.S. Pat. Nos. 3,974,240 and 3,974,241, the method of improving the flow characteristics of the blend compositions was the incorporation of a polyolefinic thermoplastic into the blend composition resulting in improvement of the flow characteristic; however, the polyolefinic thermoplastic had an adverse effect on the physical elastomeric properties of the blend composition by increasing its hardness.
The method as described in the instant invention of improving the flow characteristics of a metal neutralized sulfonated polymer by the incorporation of a silicone rubber such as polydimethylsiloxane results in a blend composition that has a proper balance of physical and rheological properties thereby enabling the user to readily extrude or injection mold the composition into a high performance elastomeric article.
The incorporation of the polydimethylsiloxane in the blend compositions permits the user to decrease the concentration levels of the preferential plasticizer which has an adverse effect on the physical properties of the composition while maintaining suitable rheological properties for an injection molding or extrusion process.